Thermoplastic compositions containing polycarbonate and polyester resins are known. Thermoplastic molding compositions containing a mixture of polycarbonate and a polyester copolymer derived from cyclohexane dimethanol and phthalic acid are also known and such compositions have been disclosed in U.S. Pat. No. 4,786,692. Characterized by their low heat distortion temperatures, high tensile and flexural strength, the compositions are said to be compatible with impact modifiers and flame retardants.
Polycarbonate resins and compositions based thereon have been extensively used in the preparation of optical storage media, such as compact discs. A critical parameter relative to such media and the molding materials therefor is their low birefringence.